\(a,\Leftrightarrow\left[{}\begin{matrix}3\left(x-2\right)=x^2-4x+6\left(x\ge2\right)\\3\left(2-x\right)=x^2-4x+6\left(x< 2\right)\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x^2-7x+12=0\\x^2-x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=3\left(tm\right)\\x=4\left(tm\right)\\x=1\left(tm\right)\\x=0\left(tm\right)\end{matrix}\right.\)
\(b,\Leftrightarrow\left[{}\begin{matrix}x^2-4x+3=x+3\left(x\le1;x\ge3\right)\\x^2-4x+3=-x-3\left(1< x< 3\right)\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x^2-5x=0\\x^2-3x+6=0\left(vn\right)\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\left(ktm\right)\\x=5\left(tm\right)\end{matrix}\right.\)
